1. Field of the Invention
The present invention relates to an inhibitor composition and, more particularly, to such a composition useful for preventing corrosion by solvents used in treating sour gas streams.
2. Setting of the Invention
The conditioning of naturally occurring and synthetic gases by absorbing acidic gases, such as CO.sub.2, H.sub.2 S, COS and HCN, in an absorbent solution has been practiced commercially for years. Aqueous solutions of various compounds such as alkanolamine, sulfolane (tetrahydrothiophene 1,1-dioxide), potassium carbonate and mixtures of two or more of these have been used for this purpose. Often, these systems are plagued by corrosion of metal equipment which can be caused by products of degradation of the absorbent, by acidic components, or by products of these acidic components with the absorbent. For example, although aqueous alkanolamine itself is not particularly corrosive toward iron and steel equipment, when dissolved CO.sub.2 H.sub.2 S are present, the solution is highly corrosive, particularly when the solution is hot.
To combat this problem, various metal compounds have been used alone or in combination with other compounds as corrosion inhibitors, e.g., compounds of arsenic, antimony and vanadium. While such metal compounds are effective corrosion inhibitors, they have the disadvantage of low solubility in most gas conditioning solutions and are of relatively high toxicity. This toxicity is particularly undesirable since it affects both the handling of the solvent and the disposal of the waste material.
One water-soluble composition for inhibiting corrosion by hydrogen sulfide, carbon dioxide and water soluble carboxylate acids comprises a quaternary ammonium compound of benzyl chloride and the residue boiling between about 200.degree. C. and about 350.degree. C. from the distillation of the acid extract of the reaction product of ammonia and acetaldehyde and a sufficient amount of a combination of surface-active agents to form a substantially clear solution when the composition is diluted with water. The surface-active combination contains about two parts of the reaction product of one mole of nonylphenol with from about 8 to 20 mole of ethylene oxide and about one part of reaction product of one mole of tridecyl alcohol with from about 30 to about 50 moles of ethylene oxide. This composition is described in U.S. Pat. No. 3,033,784 which issued on May 8, 1962 to L. W. Jones and is entitled "Water Soluble Corrosion Inhibitor and Bactericide", which is hereby incorporated by reference. Nowhere within Jones is it disclosed or suggested to use a nickel compound as a corrosion inhibitor.
Another sour gas inhibitor for CO.sub.2 promoted corrosion of iron and steel is found in U.S. Pat. No. 4,100,100 which issued on July 11, 1978 to Robert C. Clouse et al and is entitled "Cobalt Inhibitor for Sour Gas Conditioning Solutions". The inhibitor composition of Clouse comprises one part by weight of quaternary pyridine salt, about 0.001 to about 10 parts of a thio compound which is water-soluble thiocyanate or an organic thioamide and a small but effective amount of cobalt, the cobalt being present as a dissolved divalent cobalt compound. Nowhere within Clouse is it disclosed or suggested to use a nickel compound as a corrosion inhibitor.